"Banning" the comment syntax would merely ban the form of notification. People are going to look stuff up with an LLM. It's 2025; that's what we do instead of search these days. Just like we used to comment "Well Google says..." or "According to Alta Vista..."
Proscribing quoting an LLM is a losing proposition. Commenters will just omit disclosure.
I'd lean toward officially ignoring it, or alternatively ask that disclosure take on less conversational form. For example, use quote syntax and cite the LLM. e.g.:
> Blah blah slop slop slop
-- ChatGippity